Clinical Clinical Site specific IMRTSite specific IMRT

Bulent Aydogan, PhDBulent Aydogan, PhD

Department of Radiation and

Cellular Oncology

University of Chicago

Nov 2007 Antalya, Turkiye

➫ You can download the full-blown version of this talk which has site specific clinical IMRT info for H&N, Prostate and GYN from ASTRO website under the refresher courses.

➫ You can email me @

baydogan@radonc.uchicago.edu

Target AudienceTarget Audience

Everybody

New to treating with IMRTNew to treating with IMRT

Planning to treat a new sitePlanning to treat a new site

Learn from others mistakes!Learn from others mistakes!

IMRTIMRT➫ IMRT is a method of

treatment planning and delivery that conforms the high dose region to the shape of the target volume while sparing surrounding critical organs

IMRT in numbersIMRT in numbers

➫In US☣80% are using☣80% started in the last 3-4 yrs☣90% non-user are planning to

use.

➫Outside of USA ☣Turkiye!

IMRT IMRT ALARMING RPC STATISTICSALARMING RPC STATISTICS

➫ Dose accuracy☣ Recommended 3% dose and 3mm

➫ RPC IMRT validation experience (ASTRO 2006 Abstract, A. Molineau et. al.)

☣ 155 inst. 196 irradiations☣ 7% dose and 4mm DTA☣ 54 failure ~>1/3 failed (33 on dose)

IMRT IMRT

PurposePurpose➫To illustrate how various aspects of

the IMRT planning process can influence the resultant treatment plan and delivery

➫To provide an update of IMRT planning techniques for gynecologic malignancies AND H&N, prostate

➫How IGRT influence IMRT process

SummarySummary

➫ IMRT treatment planning is a multi-step process

➫ Careful consideration throughout the entire process is necessary to ensure that an optimal plan is achieved

➫ Decisions made at the time of simulation, target and tissue delineation, planning and the delivery/verification process itself impact the overall plan

Simulation – Prone vs. Supine; Type of immobilization

Target and Tissue Delineation – Multiple imaging modalities

Treatment Planning/Optimization – Number of beams/orientation

Plan Evaluation – High conformity vs. dose homogeneity

Quality Assurance – Verification of calculated dose

Treatment Delivery/Verification – Verification scheme

Treatment Planning ProcessTreatment Planning Process

SUMMARYSUMMARY➫ IGRT

☣Changing the way we do IMRTʚ Marginsʚ Biological targetingʚ Intrafraction vs. interfraction ʚ Organ motion management

٩ Gating , IID

ʚ Adaptation

☣Requires more resources and careful planning

PTV Margin and IGRTPTV Margin and IGRT

Litzenberg DW, IJROB, 65(2), 2006

General issues In Treatment General issues In Treatment PlanningPlanning

➫Dose distribution depends☣Treatment planning system / optimization☣Dose calculation method

ʚ PBC, Superposition Convolution, MC

☣ User experience☣Realistic expectations (e.g., dose constraints)

☣Beam configuration, Energy?

3 – Field

7 – Field

Number of BeamsNumber of Beams

➫ More beams = Better plan?

➫ Generally Yes☣But improvement can be

marginal over 7 beams☣Degree of improvement

depends on tumor shape and proximity to critical structures

Beam Angles and Energies Beam Angles and Energies ➫ Nearly all studies report

using 6 MV➫ Generally use 6-9 co-

planar beams➫ Avoid parallel opposed

beams➫ Beams are equidistant but

may not be uniformly distributed

➫ Non-uniform beam distribution may be used for special sites

Beam configurationBeam configuration

9 Field8 Field

User DependencyUser Dependency

Can you guess which plan is done by a experienced user?

Realistic expectationRealistic expectation

Managing Hot SpotsManaging Hot Spots“Tuning” Structures“Tuning” Structures

➫ Occasionally “hot” spots or unwanted dose in surrounding unspecified tissue

➫ Adding an additional (“tuning”) structure can reduce these “hot” spots and improve dose conformity around the PTV

➫ However, improved conformity may reduce dose homogeneity within the target

Use of “Tuning” Structure to Use of “Tuning” Structure to Improve Dose ConformityImprove Dose Conformity

Pawlicki T et al. Plan Evaluation. IMRT: A Clinical Perspective 2005

Optimizing with Optimizing with Base Plan Base Plan

Aydogan et al, TCRT, 2006

Fluence editingFluence editing

➫ It is very handy ➫Needs experience➫Exercise caution when using➫Works better for smaller hot

spots

IMRTIMRT for for

Gynecologic Gynecologic MalignanciesMalignancies

GYN IMRTGYN IMRT

➫Rationale☣Reduce volume of small bowel, bladder

and rectum irradiated☣Decrease volume of pelvic bone marrow

irradiated in patients receiving CRT☣Potentially useful in delivering higher than

conventional doses☣Alternative boost technique for patient

who are not amenable to BC

ImmobilizationImmobilization➫ Patient in supine position➫ Immobilized using alpha cradles

indexed to the treatment table

Univ of Chicago

Immobilization (Prone)Immobilization (Prone)

➫ Others favor the prone position

➫ Data from the U Iowa suggest ↑dosimetric benefits to the prone position (Adli et al. Int J Radiat Oncol Biol Phys 2003;57:230-238)

Univ of Colorado

Schefter T, Kavanagh B.Cervical Cancer: Case Study IMRT: A Clinical Perspective 2005

Planning CT ScanPlanning CT Scan➫ Scan extent: L3

vertebral body to 3 cm below ischial tuberosities

➫ Typically use 3 mm slice thickness

➫ Larger volumes used only if treating extended field whole abdomen or pelvic-inguinal IMRT

Contrast AdministrationContrast Administration

➫Oral, IV and rectal contrast are commonly used

➫ IV contrast is important to delineate vessels which serve as surrogates for lymph nodes

➫ Generally bladder contrast is not needed

Normal TissuesNormal Tissues

➫ Normal tissues delineated depends on the clinical case: In most cases, include:

Small bowel, rectum, bladder may be femoral heads

➫ In patients receiving concomitant or sequential chemotherapy, include the bone marrow (experimental)

➫ Kidneys and liver included only if treating more comprehensive fields

PTV ConsiderationsPTV Considerations➫ Organ motion in the inferior portion of the

CTV due to differential filling of the bladder and rectum

➫ Set-up uncertainty➫ Appropriate expansion remains unclear;

various reports ranging from 1 – 1.5 cm➫ At Univ of Chicago, we use a 1 cm

expansion➫ Less is known about normal tissues➫ Other centers (e.g., MD Anderson)

routinely expand normal tissues

Set-up UncertaintiesSet-up Uncertainties

➫ Dependent on type of immobilization➫ Therapist➫ University of Chicago immobilization: Alpha

cradle under legs and upper body with arms above head*

LR = 3.2 mm

SI = 3.7 mm

AP = 4.1 mm

* Haslam JJ et al. Med Dosim. 2005 Spring;30(1):36-42

Treatment Planning Treatment Planning

➫ 7-9 co-axial beam angles

(equally spaced)➫ Most centers use 6 MV➫ Comparative plans of 6 vs.

18 MV show little or no difference

➫ However, 18 MV associated with higher total body doses

➫ Prescription dose: 45-50.4 Gy☣ 45 Gy in pts receiving vaginal brachytherapy☣ 45-50.4 Gy if external beam alone

➫ 1.8 Gy daily fractions ☣ Avoids hot spots > 2 Gy

➫ “Dose painting” (concomitant boost) remains experimental☣ Potentially useful in pts with high risk factors

(positive nodes and/or margins)

Treatment PlanningTreatment Planning

Gyne IMRT - Input DVHs

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50

Dose (Gy)

PTV

Bladder

Rectum

Small Bowel

Tissue

Small bowel input DVH based on NTCP data

INPUT DVH

2.3

100

4101

1

V

NTCP

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 100 200 300 400 500 600

Volume (cc)

NTCP Analysis GYN IMRT PatientsNTCP Analysis GYN IMRT PatientsVolume receiving 45 Gy Volume receiving 45 Gy

Probability of Moderate to Severe Acute GI Toxicity Probability of Moderate to Severe Acute GI Toxicity

ConventionalPelvic RT

IMRT

Roeske et al : IJROB

IMRT Isodose DistributionIMRT Isodose Distribution

PTV

100% 70%

Acceptable UnacceptableConformity Good PoorPTV Coverage > 98% < 96%

Hot SpotsLocation Within CTV Edge of PTV

Preferably within GTV Rectal or bladder walls in ICB region

Magnitude <10% (110% dose) >20% (110% dose)<2% (115% dose) >2% (115% dose)

Cold SpotsLocation Edge of PTV Within CTV or GTVMagnitude <1% of the total dose none

Plan EvaluationPlan Evaluation

➫ A concern in the region of the vaginal cuff

➫ Two approaches are being studied at our institution to address this:☣ IGRT (CBCT)☣ Vaginal immobilization

➫ Now we simply avoid tight CTV volumes and use a 1 cm CTV→PTV expansion☣Produces very generous volumes

around the vaginal cuff

Organ MotionOrgan Motion

““Integrated Target Volume”Integrated Target Volume”

➫ A creative solution to the organ motion problem developed at MDAH

➫ Two planning scans: one with a full and one with an empty bladder

➫ Scans are then fused➫ An integrated target volume (ITV) is drawn

on the full bladder scan (encompassing the cuff and parametria on both scans)

➫ ITV is expanded by 0.5 cm → PTVITV

Small Bowel

Bladder

IntegratedTargetVolume (ITV)

PTVNodes

MD Anderson

Illustration of ITVIllustration of ITV

Rectum

Vaginal Immobilization DeviceVaginal Immobilization Device➫ Cervical and Endometrial cancer pts

treated with IM-PRT and vaginal (cylinder) HDR

➫ Goal: Use vaginal cylinder-type immobilization device and IGRT

B Aydogan, PhD – Univ of Chicago, Patent pending

Treatment table mount and indexing

IID adjustment and indexing

Adaptive approach in Gynecologic Adaptive approach in Gynecologic IMRTIMRT

➫Many cervical tumors rapidly shrink during RT (especially with concomitant chemotherapy)

➫Tight margins (CTV-to-PTV expansions) early on may be too large by the end of treatment

➫ 14 cervical cancer pts➫ MRI before RT and after 30 Gy➫ 46% ↓GTV

Impact of Tumor Regression in Impact of Tumor Regression in Cervical Cancer PatientsCervical Cancer Patients

Van de Bunt et al. Int J Radiat Oncol Biol Phys 64(1):189-96, 2006.

Bladder

Rectum

Tumor

Bladder

Tumor

Rectum

PrescriptionIsodoseWeek 1 Week 3

TumorsShrinkPlan

Adapts

IMRT <> ICB ?IMRT <> ICB ?➫ IMRT has been used to

reduce volume of normal tissues irradiated

➫ In selective sites (e.g., head and neck, prostate), IMRT has been used to deliver higher than conventional doses

➫ Can the same paradigm be applied to cervical cancer?

ApproachesApproaches

➫ SRS Boost☣ Molla et al. Int J Radiat Oncol Biol Phys 62:

118-24, 2005.

➫ Vaginal Immobilization Device☣ Aydogan B. Int J Radiat Oncol Biol Phys

65:266-73, 2006.

➫ SIB☣ Guerrero M, et al. Int J Radiat Oncol Biol Phys

62(3):933-39, 2005.

HDR vs. IMRTHDR vs. IMRTin early and recurrent endometrial cancerin early and recurrent endometrial cancer

Aydogan B. Int J Radiat Oncol Biol Phys 65:266-73, 2006.

HDR

IMRT

45 Gy

25 x 1.8 Gy

60 Gy

25 x 2.4 Gy

20 Gy

X. Allen Li, PhD – Med Col of Wisconsin

IMRT-SIB Planning IMRT-SIB Planning ApproachApproach

BMS-IMRTBMS-IMRT

➫Rationale☣CRT Improved tumor control and

survival ☣Increased toxicity in particular HT

ʚ Acute grade >2 HT is up to 50% more ʚ Acute grade >3 HT is up to 35% more

☣BMS-IMRT may reduce HT

Aydogan et al: IJROB, under review

ASTRO 2007 ARRO Poster # 2353

Dose comparison Dose comparison

BMS-IMRT DVH BMS-IMRT DVH

0%

20%

40%

60%

80%

100%

0 1000 2000 3000 4000 5000

Dose (cGy)

Vo

lum

e (

%)

4-field box

AP/PA

9F IMRT

8F IMRT

Advancement in IMRTAdvancement in IMRT

➫ NEW IMRT DELIVERY METHODS☣ Helical therapy☣ IMAT

ʚ More Conformal target dose distributionʚ Further reduction in OAR doseʚ Faster treatment

➫ NEW GENERATION TREATMENT MACHINES ☣ Online tumor tracking☣ Tumor Chasing

Courtesy : Paul Keal, Stanford Unv.

SummarySummary

➫ IMRT treatment planning is a multi-step process

➫ Careful consideration throughout the entire process is necessary to ensure that an optimal plan is achieved

➫ Decisions made at the time of simulation, target and tissue delineation, planning and the delivery/verification process itself impact the overall plan

SUMMARYSUMMARY➫ IGRT

☣Changing the way we do IMRTʚ Marginsʚ Biological targetingʚ Intrafraction vs. interfraction ʚ Organ management

٩ Gating , IID

ʚ Adaptation

☣Requires more resources and careful planning

THANKSTHANKS

➫John Roeske, PhD, Loyola University➫Arno J Mundt, MD, UCSD➫Loren K Mell, MD, Unv. of Chicago➫Brett Smith,MS, Unv. ofChicago➫Hanifi Tiryaki, PhD, Unv. of Illinois at Chicago

➫Joel Wilkie, PhD, Unv. of Chicago